The present invention relates to absorbent articles of the kind that are worn in contact with the wearer""s skin, such as diapers, incontinence protectors, sanitary napkins and like articles. The invention also relates to methods of reducing the undesired side effects that may sometimes occur when using such articles.
Absorbent articles of this kind are known in many different forms. The absorbent body of such products is conventionally produced by dry-defibring cellulose pulp, e.g. cellulose pulp in roll, bale or sheet form, and converting the dry-defibred pulp in a fluffed state to a pulp mat, sometimes with an admixture of so-called superabsorbents. Superabsorbents are polymers that are able to absorb several times their own weight of water or body fluid.
A typical problem relating to absorbent articles such as diapers, sanitary napkins, incontinence protectors or the like is that their use can lead to undesired side effects, such as skin irritation and malodours. These problems can occur as a result of occlusion, the presence of moisture, and factors of a mechanical, microbial and enzymatic nature, all of which coact with and amplify the effect of one another to different extents. For instance, several undesired side effects can occur as a result of or in conjunction with an increase in pH.
U.S. Pat. No. 3,794,034 describes the significance of pH in an absorbent article and also teaches impregnation of the article with buffering substances by means of which the pH in the article can be kept between 3.5-6.0, which is beneficial both with respect to the inhibition of the growth of undesired bacteria and therewith the occurrence of undesirable odours, and also in avoiding negative skin affects.
EP 0.311,344 describes controlling pH in absorbent articles, wherein the buffering properties are obtained with the aid of a partially neutralised superabsorbent material and an antimicrobial substance chosen from among ordinary nitrogen-based compounds or bis-guanide compounds. The undesirable side effects can be reduced, by controlling the pH of the article so that it will not exceed a given level. However, not all harmful microorganisms are influenced negatively by a low pH value. Escherichia coli, which is itself acid-producing, is an example of such a microorganism. The antimicrobial substances can also give rise to problems. For instance, these substances can give rise to allergies or skin irritation with long-time use. Moreover, general discussions are ongoing as to whether or not comprehensive use of antibiotics can result in an increasing resistance of harmful bacteria strains to antibiotics. Finally, the use of antibiotics can have negative ecological consequences with regard to the handling of waste.
Attempts to solve the aforesaid problems of undesirable odours and the growth of undesirable microorganisms have also been made by actively adding specific mricroorganisms to absorbent articles of the aforesaid kind. For example, one such technique is described in WO 97/02846. These specific microorganisms are primarily lactic acid producing bacteria, such as different species of the strains Lactobacillus and Lactococcus, which have an antagonistic effect on other microorganisms.
However, the aforedescribed known techniques have not completely eliminated the problems of undesirable odours and the growth of undesirable microorganisms. Consequently, there is a need for improvements that can further reduce the problems associated with malodours and the growth of microorganisms.
It has now surprisingly been found that the aforesaid problems associated with undesirable side effects, such as malodours and skin irritation, can be reduced still further by using an absorbent article that contains a synergistic combination of
a) a pH-regulating substance in the form of a partially neutralised superabsorbent material, and
b) lactic acid bacteria, where the pH value of said article subsequent to being wetted when worn against the skin lies in the range of 3.5-5.5, preferably within the range of 3.5-4.9, and most preferably within the range of 4.1-4.7.
The term xe2x80x9cabsorbent articlexe2x80x9d as used in this document relates to absorbent articles that are worn against the skin, such as diapers, incontinence protectors and sanitary napkins.
The term xe2x80x9csuperabsorbentxe2x80x9d and the acronym xe2x80x9cSAPxe2x80x9d relates to polymers that are able to absorb several times their own weight of water or body fluid. A suitable partially neutralised superabsorbent material may be comprised of a cross-linked polyacrylate of the kind described in EP 0,392,108, although other types of superabsorbent material that have corresponding properties may alternatively be used.
The term xe2x80x9clactic acid bacteriaxe2x80x9d and the abbreviation xe2x80x9cLBxe2x80x9d relate to a group of bacteria which produce lactic acid at normal fermentation. Examples of bacteria species that include strains belonging to this group are Lactobacillus, Lactococcus, Leuconostoc and Pediococcus. Bacteria of the families Lactobacillus and Lactococcus are preferred.
The term xe2x80x9cCTMPxe2x80x9d relates to chemithermomechanical pulp.
The Term xe2x80x9cCPxe2x80x9d relates to chemical cellulose pulp.
The term cfu relates to colony-forming units.